1. Field of the Invention
The present invention relates to a zoom strobe device (a built-in type zoom strobe device) which can be advantageously incorporated in a camera.
2. Description of the Related Art
In accordance with miniaturization of recent compact zoom cameras (LS zoom cameras), miniaturization of a built-in strobe device is also required. In a built-in zoom strobe device, a flash coverage (illumination angle) is varied by varying the distance between a reflector which is provided the base thereof with a rod-shaped light emitting tube and a Fresnel lens. The illumination angle is reduced as the distance between the Fresnel lens and the reflector (rod-shaped light emitting tube) is increased.
In such a zoom strobe device, if the flash coverage of illumination is increased in accordance with a super wide angle of the camera, a large space is necessary. In particular, the size in the upward/downward direction must be increased relative to the size in the forward/rearward direction with respect to the thickness direction of the camera, thus resulting in difficulty in miniaturization of the camera. Furthermore, if a zoom ratio is increased, it is difficult to increase the guide number on the telephoto side (small flash coverage side). If a large guide number on the telephoto side is reserved, the marginal illumination on the wide angle side (large flash coverage side) is insufficient.
The present invention provides a small zoom strobe device in which sufficient illumination can be obtained from the wide angle side to the telephoto side and from the central area to the marginal area and is suitable for a super wide angle.
According to an aspect of the present invention, a zoom strobe device suitable for a super wide angle is provided, including a reflector, a rod-shaped tubular light emitting tube, and a Fresnel lens. A distance between the reflector, which is provided on the base thereof with the rod-shaped tubular light emitting tube, and the Fresnel lens is varied to vary a flash angle of illumination, wherein the zoom strobe device satisfies the following conditions (1) and (2):
0.08 less than xcfx86xc3x97Lw less than 0.15xe2x80x83xe2x80x83(1); 
0.70 less than Lw/H less than 0.85;xe2x80x83xe2x80x83(2); 
wherein
xcfx86 designates the resultant power of the Fresnel lens in an upward/downward direction perpendicular to the length of the rod-shaped light emitting tube,
Lw designates the distance between the base of the reflector and an outer surface of the Fresnel lens when the reflector is located closest to the Fresnel lens, and
H designates the maximum length of the strobe device in the upward/downward direction.
It is desirable for the zoom strobe device to satisfy the following condition (3):
1.2 less than Lt/H less than 1.5xe2x80x83xe2x80x83(3); 
wherein
Lt designates the distance between the base of the reflector and an outer surface of the Fresnel lens when the reflector is located farthest from the Fresnel lens.
In practice, a zoom strobe device suitable for a super wide angle can be incorporated in a zoom compact camera.
The present disclosure relates to subject matter contained in Japanese Patent Application No. 2002-239594 (filed on Aug. 20, 2002) which is expressly incorporated herein by reference in its entirety.